At present, the standardization of 4G wireless communication system is being carried out in 3GPP (Third Generation Partnership Project). The 4G makes it possible to use techniques such as a relay or carrier aggregation, thereby improving the maximum communication speed and the quality at cell edges. Further, it also has been studied to improve the coverage by introducing a base station other than eNodeB (macrocell base station), such as HeNodeB (Home eNodeB, femtocell base station, small base station for mobile phone) or RHH (Remote Radio Head).
In such a wireless communication system, user equipments are frame-synchronized with a base station based on a synchronization signal transmitted from the base station, and then an internal oscillator of the user equipment is synchronized with an oscillator of the base station with high accuracy. Then, the user equipment periodically receives signals transmitted from the base station and causes the internal oscillator of the user equipment to be matched to the oscillator of the base station.
If there is any discrepancy between the internal oscillator of the user equipment and the oscillator of the base station, then reception and transmission may not be performed at an accurate frequency and time, and thus the accuracy of the internal oscillator of the user equipment is important. Further, the structure of a frame that a base station shares with user equipments is described, for example, in Patent Literature 1.
In order for a base station to simultaneously receive wireless signals transmitted from a plurality of user equipments, each of the user equipments performs an adjustment to the length of time according to the distance between the base station and the user equipment, which is called Timing Advance. Specifically, the Timing Advance is performed in the procedure of random access in which the user equipment transmits a preamble toward a random access window. A Timing Advance value can be obtained from a relationship between an arrival time of the preamble at a base station and the random access window.
Meanwhile, there has been a discussion concerning the MTC (Machine Type Communications) in 3GPP. As an application of MTC, a variety of applications such as Metering for collecting information relevant to water systems or power systems, Health for collecting information relevant to health care instruments, or the like have been studied. The MTC terminal is a terminal designed specifically for these applications.
Furthermore, the MTC terminal has characteristics such as Time Controlled, Online Small Data Transmission, for example. That is, it is expected that the MTC terminal is kept in an idle mode for a large amount of time, and receives signals from a base station or transmits small pieces of information to a base station in a burst manner. In addition, because low power consumption is required for the MTC terminal, it is desirable to keep the length of time taken up by the burst transmission and reception as short as possible. Further, it is considered that the burst transmission and reception are performed in a very long period of interval once every few hours or once every few days, not a period of the order of a few ms or tens of ms at which an existing LTE terminal receives a paging channel.